The compactness is determined by whether the tile-making equipment is advanced or not and the production technology level. High-density tiles must be made of high-pressure (about 1250 newton force) semi-dry cement. The water-cement ratio of cement is 0.4~0.5 (0.4~0.5 kg of water is added to one kilogram of cement), which is automatically prepared by American patented mixing equipment (other simple mixing methods can't reach it). In production, cement is extruded and rolled on the high-strength aluminum alloy die in the rolling bin like steel rolling, and then automatically cut off to form a high-density tile blank. Because of the small internal gap, water is not easy to penetrate. Small factories generally use parallel extrusion equipment to manufacture, manually mix materials or use general simple mixers. Only when the water-cement ratio is increased to 0.6~0.7 can the cement slurry be mixed. Coupled with the use of iron mold, can not bear a lot of pressure, can only be achieved overnight, so the density is greatly reduced, and the internal cracks are large and many, so the impermeability is very poor. On cloudy days, rain will seep into the back of the tile and drip down, and then seep into the roof. According to the data, when the water-cement ratio of cement increases from 0.4 to 0.7, the impermeability decreases by 100 times! ! ) low density, not only poor impermeability, but also decreased strength. The flexural strength of good tiles can reach more than 300 kg, and that of poor tiles is less than 100 kg. Poor impermeability and no frost resistance in winter. Especially in the north, snow water seeps into tiles during the day and freezes and expands at night, which will cause tiles to crack and gradually peel off, and the service life of tiles is not long. It determines the strength, water resistance, frost resistance and service life of ceramic tiles.